Stabilized lubricating oil



Patented Apr. 28, 1942 res PT-NT OFFICE 2,281,521 g STABILIZED LUBRICATING on.

Everett W. Fuller, Woodbury,-N. J., assignor to Socony-Vacuum Oil Company, Incorporated. New York, N. .Y., a corporation of lflew York No Drawing. Application October 8, 1940,

' Serial No. 360,289

9 Claims.

- tions of use.

As is well known to those familiar with the art, substantially all of thevarious fractions obtained from mineral oils are susceptible to oxidation. This susceptibility of anoil fraction to oxidation and the manner in which the oxidation manifests itselfwithin the oil varies with the oil fraction, viscous oils such as lubricants and dielectrics being distinguished from nonviscous fractions such as gasoline and kerosene. It also varies with the type and degree of refinement to which the oil fraction has been subjected and the conditions under which the oil is used or tested. In other words, the products formed in a mineral oil fraction as a result of oxidation and the degree to which they are formed under given conditions depends upon the chemical character of various unstable constituents or constituents which may act as oxidation catalysts in a particular fraction. It naturally follows that the formation of the undesirable oxidation products in a refined viscous oil is dependent upon the extent to which the constituents which tend toward their formation have been removed by refining operations.

A highly refined viscous oil, for'example, which is one that has been refined by treatment with fuming sulfuric acid or other means or combinations such as A1013, solvents and acids (or with large quantities of concentrated sulfuric acid), tends to form relatively large amounts corrosive to metals and thus reduce the useful life of the. oils-as lubricants or for other purposes in which they come in contact with metals,

and the acidic materials are also injurious in textile lubricants and in spray oils.

Moderately refined oils-that is, oils that have been refined by treatment with only moderate amounts of sulfuric acid or other refining agents-tend to form relatively small amounts of acidic oxidation products, as compared with highly refined oils, but they undergo material color depreciation and form considerable amounts of sludge. The changes taking place in these oils are appreciably accelerated by the presence of metal catalysts such as copper. Sufficient acid is generally formed to cause some reduction in the dielectric strength of these oils, but the principal objection to them is their tendency to deposit sludge which interferes with heat transfer in transformers and turbines and also causes plugging of oil feed linesin lubricating systems.

Solvent-refined oils in general, which have been prepared by treatment with selective solvents such as chlorex, phenol, furfural, etc., re-

semble the moderately refined acid-treated oils in that their oxidation is accelerated by the pres-- highly refined-oils. Both sludge and acid formation lower their value for many purposes such as electrical insulation, lubrication, etc. Also,

solvent-refined oils have found extensive use as lubricants for internal combustion engines because of their high viscosity index, but under the conditions of use encountered in crankcases 40 such oils develop constituents which are-corrosive toward certain metal bearings such as the cadmium-silver alloys and other bearing alloys of similar corrosion-susceptibility which are sometimes used. V

It is to be understood that this classification of. oils is by no means limiting and that bodies results, which tends to lower the dielectric strength of the oils and has other harmful effects which are undesirable. The acids are there ,can' exist viscous mineral oils whose refining and blending has been such as to make them intermediate in properties between the types set up. Thus,.response to inhibitors maybe said to depend entirely upon the type of oxidation and end products of oxidation of an oil, which duce highly refined oils than. the Coastal type of oils.

The use of oxidation inhibitors .for the purpose of stabilizing a viscous mineral oil fraction against the deleterious effects of oxidation discussed above is well known. Since the action of these inhibiting materials is apparently catalytic, the problem of their development is a difficult one and is evidently influenced to a large degree by the oxidizable constituents which are in the oil following a particular refining treatment. Thus, a particular inhibitor or class of inhibitors may be effective to stabilize a highly refined oil against acid formation while the same inhibitor may have no appreciable effect upon acid, color or sludge formation in a mod erately refined oil and vice versa. This same inhibitor may or may not be efiective in inhibiting' acid, sludge, and color formation in a solvent-refined oil and may or may not be effective to inhibit the corrosive action of a solvent-refined oil toward bearing metals having the corrosion-susceptibility of cadmium-silver alloys. Furthermore, the behavior of an inhibitor ina non-viscous mineral oil traction does not necessarily afiord any indie tion as to what its effect will be in a viscous oi fraction.

The present invention is predicated upon the discovery of a novel class of compounds or reaction products which are efiective to stabilize viscous mineral oil fractions, typified by the various types of oils discussed above, against the deteriorating effects of oxidation encountered in the use of such oils. The class of compounds or reaction products contemplated lierein'as mineral oil-improving agents are those which are 'pbtainable by reacting in substantially equimolecular proportions an aromatic amine, a mercaptan and formaldehyde. It is thought that the principal reaction involved in the preparation of" these reaction products may be represented by the following general equation:

. for petroleum oils, and I do not, therefore, wish to be bound by any theory as to the reaction or reactions involved or the chemical composition of the reaction product but prefer to designate the stabilizer contemplated herein as the reaction product of an aromatic amine, a mercaptan and formaldehyde; The reaction may be run in a neutral medium or in the presence of an inorganic acid such as hydrochloric acid.

Further details in the procedures which may be followed in synthesizing the stabilizing agents contemplated herein may be obtained from thefollowing illustrative examples.

EXAIWPLE ONE Twenty-four grams of ethyl aniline (0.2 mole) and 20.3 grams of amyl mercaptan (0.2 mole) were dissolved in 200 cc. of methyl alcohol. Bwenty-eight grams of concentrated HCl and 17 grams of formaldehyde solution (approximately 0.2 mole) were added, and the mixture was allowed to stand at room temperature for 4 days. The clear brown liquid was then poured into 1000 cc. of water containing 20 grams of sodium hydroxide. The oil separating was extracted with benzol, washed with water, and the benzol layer was dried over calcium chloride. vThe benzol was then distilled off, and the oil remaining was distilled under a vacuum of 2 mm. pressure. The fraction coming over at 146-148 C. was a yellow oil that contained 13.7 per cent sulfur (theoretically sulfur content of CsHnSCI-IzCsI-IqNHCzHs is 13.5 per cent).

EXAMPLE TWO Twenty-four grams of ethyl aniline (0.2 mole) and 22 grams" of thiophenol (0.2 mole) were dissolved in 200 cc. methyl alcohol. Twentyeight grams of concentrated HCl and 1'7 grams of formaldehyde solution (approximately 0.2 mole) were added, and the mixture was allowed to stand at room temperature for, several days. It was then poured into water containing suil'lcient sodium hydroxide to neutralize the acid, and the oil separating was taken up in benzol, water-washed, dried, and the benzol then evaporated oil. This left an oil which on standing partly solidified. On recrystallization from methyl alcohol a solid was obtained that melted at -81 C., and an analysis gave 12.9 per cent sulfur (theory for C6H5SCH2C6H4NHC2H5 is 13.1 per cent S.)

EXAMPLE THREE Twenty-four grams of ethyl aniline (0.2 mole) were dissolved in 200 cc. of ethyl alcohol, and 33.4 grams of mercapto benzothiazole (0.2 mole) were added. Sixteen grams of 38 per cent formaldehyde solution (approximately 0.2 mole) were added to the well stirred mixture. There was a slight rise in temperature. The mixture was then warmed to about 60 (3., and the mercapto benzothiazole, which had been mostly in suspension in the alcohol, gradually went into solution. The mixture was allowed to stand at room temperature :for three days. Itthen contained a viscous oil atthe bottom of the flask. The contents of the flask were poured into 1000 cc. of water, which gave a very viscous oil. This was extracted with benzol, the benzol layer was washed with water, dried over CaClz and the benzol evaporated off. This left a very viscous oil that gave 20.3 per cent sulfur on analysis (theory for C2H5NHC6H4CI'I2SCSNC6H4 is 21.3

per cent S.)

EXAMPLE FOUR 46.6 grams of diamyl aniline (0.2 mole), 20.8

' separating was taken up in benzol, washed with 10 per cent NaOH solution, and then with water and dried over CaClz. The benzol was then distilled oif, and the remaining oil was heated to a pot temperature of 210 C. at-2 mm. pressure to remove unreacted materials. The residue consisted of a viscous oil that contained 9.49 per cent sulfur (theory for (C5H11) 2NC6H4-CH2.SC5H11 is 9.2 per cent S.)

The foregoing examples are merely illustrative of typical reaction products and procedures which may be followed in their preparation. The invention is not to be construed as limited to the procedures or reactants given in the examples but is directed to mercaptans generally and aromatic amines generally as compounds which may be reacted with formaldehyde to obtain these oil addition agents. Examples of other aromatic amines which may be used in preparing these reaction products are: aniline, paraphenylene 'diamine, alpha-naphthylamine, beta-naphthylamine, N- phenyl beta naphthylamine, etc. Other typical examples of mercaptans are: methyl mercaptan, ethyl mercaptan, butyl mercaptan, hexyl mercaptan, benzyl mercaptan, thiocresol, thiobetanaphthol, etc. Other materials which may be used as the solvent medium for the reaction mixture are propyl alcohol, acetone, benzol, etc., and it is to be understood that the time and temperature of the reaction may be varied over relatively wide limits.

To demonstrate the effectiveness of the general class of reaction products contemplated herein as addition agents for mineral oils, several typical products have been prepared and tested in various viscous mineral oil fractions. The results obtained, together with a brief description of the oil and test'procedure used, are set'forth in the following examples. The addition agents used in these examples and indicated by the letters A, B, etc., were prepared from the reactants as listed in Table I below, which were used in substantially equimolecular proportions. It will be observed that the preparations were made both with and without an inorganic acid.

' Table I Reactants Ethylaniline-l-amyl mercaptan-I-CHM (+HC-l) Para-phenylene diamine+amy1 mercaptan+0l1z0 (+HC1). Ethyl aniline+benzyl mercaptan-l-CHzO (+1101).

egemon c EXAMPLE FIVE (-I-IIGHLY REFINED OTL) The oil used in this test was a highly refined oil suitable for use in transformers which had been prepared by treating a Coastal distillate with 40 pounds of 98 per cent sulfuric acid and 180 pounds of 103 per cent oleum per barrel; followed by washing "and clay percolation. It had a specific gravity of 0.871, a flash point of 310 F., and a S. U. viscosity of 69 seconds at 100 F. This type of Oil tends to form acidic products of oxidation. It was tested by heating samples to 120 C. and bubbling oxygen through them for 70 hours. The acids thus formed were determined by titrating with alcoholic KOH. Re-

sults obtained with samples of the blank oil and the oil with typical addition agents (from Table I above) of the type contemplated herein are iven in Table 11 below, in which the N. N. value represents the milligrams of KOH needed'to neutralize the acids in 1 gram of oil.

EXAMPLE SIX (MoDuRA'rELY REFINE!) OIL) The oil used in this series of tests was a mixed Mid-Continent and Coastal distillate which had been refined by treatment with 70 pounds of 98 per cent sulfuric acid per barrel, neutralized, washed and percolated through clay. It had a specific gravity of 0.879, a flash point of 385 F., and a S. U.- viscosity of 152 seconds at 100 F. It is an oilsuitable for use in turbines. The test involved maintaining a 295-00. sample of the oil (or oil blend) at a temperature of 200- F. with 5 liters of air per hour bubbling there through. Each sample contained 24 inches No.

18 gauge copper wire and 1 gram of iron gran- I ules, and 2 cc. of distilled water were added each day. The samples were tested after varying intervals for acidity, color, and sludge, and the results for the blank oil and blends of same containing typical addition agents of the type contemplated herein are set forth in the following table.

Table III l I Percent Time, Lov. Sludge, Adam agent used hours color mg./25cc.

l '1 13 6 68 25 17 240 2.5 110 246 336 16.0- 400 1,282 161 .02 5 2 D .10 491 .s 31 12 1,513; 2.4 115 187 .s 30 E ego 6.22 14; 429 1 s M 491 6.1 280 167 .01 9 18 J .10 503 .10 15 1 1,1 13; 1.1 1 32 32 s 5 K 500 3.4 15 132 167 .02 2 4 L .10 503 2.1 45 13 1,001 5.4 382 EXAMPLE SEVEN (SOLVENT-Barman OIL) The oil used in this test was a distillate from a Rodessa crude which had been refined with furfuraL- dewaxed, and filtered. It had a specific gravity of 0.856, a flash point of 420 F., and a S. U. viscosity of 151 seconds at 100 F. The'test procedure was the same as that described in Example Six. The results are given in the following table.

Table IV Percent Time Lov. Sludge, Addltwn agent used hours color mg./25cc.

1 2 B 332 16.3 9s 81 105 0.0 1 3 K .10 500 .01 2 r? 2 D 32c 14. 4 105 107 F .10 122 1.3 g 32 G 32 16:31 10g 13g 1 H 10 404 12. 0 as 101 164 0.0 1 4 I .02 49s .01 2 7 856 .22 0 14 L .10 102 0.0 1 0 EXAMPLE EIGHT (Gonnosron Tas'r) The oil used in this test was a. solvent-refined S. A. E. 20 grade motor oil, which is normally corrosive to hearing metalshaving the corrosionsusceptibility of cadmium-silver alloys. The oil was tested by placing a section of a bearing containing a cadmium-silver alloy surface and weighing about 6 grams in a sample of the oil- (or oil blend) and heating the oil sample to a temperature of 175 C. for a period of 22 hours while bubbling a stream of air therethrough Table V Percent used Mg. loss in weight Addition agent Uninhibited Inhibited I The amount of addition agent used may be varied, depending upon the character of the oil and the conditions which it will encounter in' used. In general it appears that satisfactory results are obtained with the reaction products disclosed herein in amounts ranging from about .01

aforesaid, these characteristics of a viscous 75 accuser mineral oil fraction. are governed by the crude stoclr from which the oil is obtained, as well as by the refining treatment; and it is possible, for example, to obtain a highly refined oil from a selected crude stock by a refining treatment which would yield a moderately refined oil from another crude stock.

I claim:

1. A lubricating oil composition comprising a viscous hydrocarbon oil which normally tends to deteriorate by oxidation under normal conditions of use and in intimate admixture therewith a minor proportion, suiiicient to inhibit such deterioration, of a reaction product obtainable by reacting substantially equimolecular proportions of a mercaptan, an aromatic amine and formaldehyde.

2. A lubricating oil composition comprising a vnscous hydrocarbon oil which normally tends to deteriorate by oxidation under normal conditions of use and in intimate admixture therewith a minor proportion, sufiicient to inhibit such deterioration, of a reaction product obtainable by reactingin the presence of an inorganic acid substantially equimolecular proportions of a mercaptan, an aromatic amine and formalde hyde.

3. A lubricating oil composition comprising a viscous hydrocarbon oil which normally tends to deteriorate by oxidation under normal conditions of use and in intimate admixture therewith 1 a minor proportion, sufiicient to inhibit such deterioration, of a reaction product obtainable by reacting substantially equimolecular propertions of formaldehyde, a mercaptan and an aromatic amine selected from the group consisting of ethyl aniline, diamyl aniline, beta-naphthylamine, butyl-alpha-naphthylamine, phenylalpha-naphthylamine, and paraphenylene diamine.

4. A lubricating oil composition comprising a viscous hydrocarbon oil which normally tends to deteriorate by oxidation under normal conditions of use and in intimate admixture therewith a minor proportion, suflicient to inhibit such deterioration, of a reaction product obtainable by reacting substantially equimolecular proportions of formaldehyde, an aromatic amine and a mercaptan selected from the group con sisting of butyl mercaptan, amyl mercaptan, benzyl mercaptan, thiophenol, and mercapto benzothiazole.

5. A lubricating oil composition comprising a viscous hydrocarbon oil which normally tends to deteriorate by oxidation under normal conditions of use and in intimate admixture therewith a minor proportion, sufficient to inhibit such deterioration, of a reaction product obtainable by reacting substantially equimolecular propor-= tions of formaldehyde, a mercaptan selected from the group consisting of butyl mercaptan, amyl mercaptan, benzyl mercaptan, thiophenol,

and mercapto benzothiazole, and an aromatic '7. A lubricating oil composition comprising a r 2 L5 1 viscous hydrocarbon oil-which normally tends to deteriorate by oxidation under normal conditions of use and in-intimate admixture therewith deterioration; of anorganic reaction product having the probable formula:

H ms-c-a-N in which R, represents an aromatic nucleus, R1 is selected from the group consisting of alkyl, aryl, aralk'yl and alkaryl radicals, and R2 and Rs are selected from the group consisting of hydro- 1 gen, alkyl, aryl, aralkyl and alkaryl;

- a minor proportion, suflicient to inhibit. such deteriorate by oxidation under normal condi- "tionsof use and in intimate admixture therewith a minor proportion, sufiicient to inhibit such deterioration, of a reaction, product obtainable byreacting substantially equimolecular pro-' portions of an aromatic amine, butyl mercaptan and formaldehyde. I

'9. A lubricating oil composition comprising a "viscous hydrocarbon oil which normally tends to deteriorate by oxidation under normal con- 7 ditions of and in intimate admixture therewith a. minor proportion, suflicient to inhibit 8. A lubricating oil composition comprising a viscous hydrocarbon oil which normally tends to butyl mercaptan 

